Optical transmission technology development trends present a single channel, a higher rate (e.g. single channel transmission at a rate of 400 G/1 T), higher frequency spectral efficiency and a high-order modulation mode, thereby the clearest and the most important direction of the development for the optical transmission is still to continue improving the rate. The high speed transmission faces with many restrictions, there are two main aspects: on one aspect, the optical transmission technology develops to high frequency spectral efficiency convergence transmission and high service interface transmission, if the frequency spectral efficiency cannot continue to be improved, the retransmission converging from a low speed to a high speed makes little sense, since there may be a high speed Ethernet interface at client side, it still needs to consider the problem of the high speed interface transmission, 400 G will be a critical point in the spectrum efficiency limit; in another aspect, the optical transmission technology develops to a long distance (a long span and multiple spans), although a system Optical Signal to Noise Ratio (OSNR) is improved by means of adopting a low-loss fiber, a low noise amplifier, and reduction of span spacing, etc., but the improvement is limited and it is difficult to achieve a significant breakthrough and implement in engineering.
With the increasing demand for the bearer Network bandwidth, the Beyond-100 G technology has become a solution for solving the increasing demand for the bandwidth, above the 100 G, no matter it is 400 G or 1 T, Wavelength Division Multiplexing (WDM) of the conventional 50 GH Fixed Grid cannot provide sufficient frequency spectrum width to achieve the Beyond-100 G technology. Due to the defects of the fixed grid, it is needed to propose a wider flexible grid. In the related art, multiple rates maxing transmission of the beyond-100 G and the flexibility of the modulation mode for the beyond-100 G case to different demands for the channel bandwidths, if an appropriate bandwidth is tailored for each channel, it can realize the full use of the system width, thereby resulting in a flexible grid system. For the demand for a ultra-high speed WDM system based on the increasing bandwidth demand, thereby a demand for the Flexible Grid technology is introduced, the introduction of the Flexible Grid technology will result in that frequency spectrum fragments will occur. The beyond-100 G service, for example, when the Ethernet service of a 1 T rate are transmitted on an optical layer, it is impossible to find a successive frequency spectrum, of which frequency spectrum width is large enough, to transmit the service, thereby it is needed to inversely multiplex a electrical layer container of a 1 T rate to a plurality of non-successive frequency spectrum to be transmitted, therefore the frequency spectrum utilization can be improved and frequency spectrum fragment resources will be used as much as possible. In addition, optical devices for coherent receiving technology are provided, the optical devices can dynamically and correctly receive optical signals according to configured information to be received, such as the center frequency, frequency spectral width and modulation mode, etc.
After the inverse multiplexing is introduced in the related art, the problem of subframe misordering occurs, which causes that the receiving node cannot assemble the subframes into a complete frame after receiving the subframes, at present, the effective solution about how to determine, by a receiving node, whether the subframe misordering occurs, has not been proposed yet.